1. Field of the Invention
The present invention relates to a static bearing conveying apparatus having magnetically preloading and motional error correcting functions. More particularly, the present invention relates to a static bearing conveying apparatus, which comprises a table and a guide having simple construction, and which is adapted to generate preload using magnetic force and to adjust a floating gap through variation in magnetic force applied to generate the preload, thereby providing magnetically preloading and motional error correcting functions.
2. Description of the Related Art
Preload for static bearings is generated by magnetic force of a permanent magnet, and the magnetic force is varied to maintain a floating gap of the static bearings by use of an electromagnetic coil. This construction is based on the fact that the rigidity of the static bearings based on the preload is inversely proportional to the floating gap.
Specifically, the floating gap required for the static bearings can be adjusted by changing the intensity of magnetic force through change of electric current applied to the electromagnetic coil, and errors in angular motion and in linear motion horizontal to a conveying direction of a conveying system can be corrected according to structure of a correcting unit.
In FIG. 1, a conventional conveying system employing static bearings is shown. As an example of the conventional conveying system, a double-sided pad type conveying apparatus comprises a guide 20 located below a table 10 to maintain sufficient rigidity of the static bearings and having guide surfaces 21 and formed on opposite sides thereof to guide the static bearings, and a pair of bearing pads 30 fixed in parallel to each other on the table 10 while facing the guide surfaces 21 and 22.
Thus, machining errors on the guide surfaces 21 and 22 requiring precise machining directly affect motional errors in conveyance, which causes motional precision of the table to be lowered.
In addition, since the guide surfaces 21 and 22 must be identically formed on both sides of the guide, machining costs are increased, and since the conventional conveying system requires the pair of pads 3a and 3b, manufacturing costs thereof are also increased.